The role of tunneling nanotubes during early stages of HIV infection and reactivation: implications in HIV cure

Something to talk about; crosstalk disruption at the neurovascular unit during HIV infection of the CNS

Although treatable with antiretroviral therapy, HIV infection persists in people living with HIV (PLWH). It is well known that the HIV virus finds refuge in places for which antiretroviral medications do not reach therapeutic levels, mainly the CNS. It is clear that as PLWH age, the likelihood of developing HIV-associated neurological deficits increases. At the biochemical level neurological dysfunction is the manifestation of altered cellular function and ineffective intercellular communication. In this review, we examine how intercellular signaling in the brain is disrupted in the context of HIV. Specifically, the concept of how the blood-brain barrier can be a convergence point for crosstalk, is explored. Crosstalk between the cells of the neurovascular unit (NVU) (endothelium, pericytes, astrocytes, microglia and neurons) is critical for maintaining proper brain function. In fact, the NVU allows for rapid matching of neuronal metabolic needs, regulation of blood-brain barrier (BBB) dynamics for nutrient transport and changes to the level of immunosurveillance. This review invites the reader to conceptually consider the BBB as a router or convergence point for NVU crosstalk, to facilitate a better understanding of the intricate signaling events that underpin the function of the NVU during HIV associated neuropathology.

Tunneling nanotubes and tumor microtubes-Emerging data on their roles in intercellular communication and pathophysiology: Summary of an International FASEB Catalyst Conference October 2023

In the past decade, there has been a steady rise in interest in studying novel cellular extensions and their potential roles in facilitating human diseases, including neurologic diseases, viral infectious diseases, cancer, and others. One of the exciting new aspects of this field is improved characterization and understanding of the functions and potential mechanisms of tunneling nanotubes (TNTs), which are actin-based filamentous protrusions that are structurally distinct from filopodia. TNTs form and connect cells at long distance and serve as direct conduits for intercellular communication in a wide range of cell types in vitro and in vivo. More researchers are entering this field and investigating the role of TNTs in mediating cancer cell invasion and drug resistance, cellular transfer of proteins, RNA or organelles, and intercellular spread of infectious agents, such as viruses, bacteria, and prions. Even further, the elucidation of highly functional membrane tubes called "tumor microtubes" (TMs) in incurable gliomas has further paved a new path for understanding how and why the tumor type is highly invasive at the cellular level and also resistant to standard therapies. Due to the wide-ranging and rapidly growing applicability of TNTs and TMs in pathophysiology across the spectrum of biology, it has become vital to bring researchers in the field together to discuss advances and the future of research in this important niche of protrusion biology.

Mechanisms of Intracellular Communication in Cancer and Pathogen Spreading

Cell-to-cell interactions are essential for proper development, homeostasis, and complex syncytia/organ formation and function. Intercellular communication are mediated by multiple mechanisms including soluble mediators, adhesion molecules and specific mechanisms of cell to cell communication such as Gap junctions (GJ), tunneling nanotubes (TNT), and exosomes. Only recently, has been discovered that TNTs and exosomes enable the exchange of large signaling molecules, RNA, viral products, antigens, and organelles opening new avenues of research and therapeutic approaches. The focus of this review is to summarize these recent findings in physiologic and pathologic conditions.

Tunneling Nanotubes: The Cables for Viral Spread and Beyond

Multicellular organisms require cell-to-cell communication to maintain homeostasis and thrive. For cells to communicate, a network of filamentous, actin-rich tunneling nanotubes (TNTs) plays a pivotal role in facilitating efficient cell-to-cell communication by connecting the cytoplasm of adjacent or distant cells. Substantial documentation indicates that diverse cell types employ TNTs in a sophisticated and intricately organized fashion for both long and short-distance communication. Paradoxically, several pathogens, including viruses, exploit the structural integrity of TNTs to facilitate viral entry and rapid cell-to-cell spread. These pathogens utilize a "surfing" mechanism or intracellular transport along TNTs to bypass high-traffic cellular regions and evade immune surveillance and neutralization. Although TNTs are present across various cell types in healthy tissue, their magnitude is increased in the presence of viruses. This heightened induction significantly amplifies the role of TNTs in exacerbating disease manifestations, severity, and subsequent complications. Despite significant advancements in TNT research within the realm of infectious diseases, further studies are imperative to gain a precise understanding of TNTs' roles in diverse pathological conditions. Such investigations are essential for the development of novel therapeutic strategies aimed at leveraging TNT-associated mechanisms for clinical applications. In this chapter, we emphasize the significance of TNTs in the life cycle of viruses, showcasing the potential for a targeted approach to impede virus-host cell interactions during the initial stages of viral infections. This approach holds promise for intervention and prevention strategies.